Predicting the Oxidation/Corrosion Performance of Structural Alloys in Supercritical CO2
- Wright HT Inc., Denver, CO (United States)
- Electric Power Research Inst. (EPRI), Charlotte, NC (United States)
This project was the first research to address oxidation of alloys under supercritical CO2 conditions relevant to a semi-open Allam Cycle system. The levels of impurities expected in the CO2 for typical operation were determined by thermodynamic and mass balance calculations, and a test rig was assembled and used to run corrosion tests at temperatures from 650 to 750°C in CO2 at 200 bar for up to 5,000h, with and without impurities. Oxidation rates were measured for seven alloys representing high-strength ferritic steels, standard austenitic steels, and Ni-based alloys with higher-temperature capabilities. The very thin, protective scales formed on the high-temperature alloys provided significant challenges in characterization and thickness measurement. The rates of mass gain and scale thickening were possibly slower when oxidizing impurities were present in the sCO2, and the scale morphologies formed on the ferritic and austenitic steels were consistent with expectations, and similar to those formed in high-pressure steam, with some potential influences of C. Some surface hardening (possibly due to carbon uptake) was identified in ferritic steels Grade 91 and VM12, and appeared more severe in commercially-pure CO2. Hardening was also observed in austenitic steel TP304H, but that in HR3C appeared anomalous, probably the result of work-hardening from specimen preparation. No hardening was found in Ni-base alloys IN617 and IN740H. An existing EPRI Oxide Exfoliation Model was modified for this application and used to evaluate the potential impact of the scales grown in sCO2 on service lifetimes in compact heat exchanger designs. Results suggested that reduction in flow area by simple oxide growth as well as by accumulation of exfoliated scale may have a major effect on the design of small-channel heat exchangers. In addition, the specific oxidation behavior of each alloy strongly influences the relationship of channel wall thickness to service lifetime.
- Research Organization:
- Electric Power Research Inst. (EPRI), Charlotte, NC (United States)
- Sponsoring Organization:
- USDOE Office of Fossil Energy (FE)
- Contributing Organization:
- Det Norske Veritas USA, Inc Oak Ridge National Laboratory Wright HT Inc
- DOE Contract Number:
- FE0024120
- OSTI ID:
- 1415286
- Report Number(s):
- DOE-EPRI-24120
- Country of Publication:
- United States
- Language:
- English
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